Botrytis Bunch Rot Botrytis Bunch Rot Botrytis cinereaBotrytis cinerea

Dollars and SenseDollars and SenseJanuary 17, 2007January 17, 2007Santa Rosa, CASanta Rosa, CA

W. D. GublerW. D. GublerDepartment of Plant PathologyDepartment of Plant PathologyUniversity of California, DavisUniversity of California, Davis

Disease TriangleDisease Triangle

►Pathogen- Pathogen- Botrytis cinereaBotrytis cinerea►Environmental ConditionsEnvironmental Conditions►HostHost►TimeTime

EpidemiologyEpidemiology

►Fungus is ubiquitousFungus is ubiquitous►Fungus is a weak pathogenFungus is a weak pathogen►Attacks juvenile tissue, highly succulent Attacks juvenile tissue, highly succulent

and senescent tissue such as blossom and senescent tissue such as blossom parts, ripe fruit and injured or dead parts, ripe fruit and injured or dead tissues.tissues.

►After infection the fungus can survive as a After infection the fungus can survive as a saprophyte on dead tissue or can produce saprophyte on dead tissue or can produce sclerotia (resistant resting structure).sclerotia (resistant resting structure).

EpidemiologyEpidemiology

► The fungus can be associated with debris on The fungus can be associated with debris on the vine or on the vineyard floor:the vine or on the vineyard floor: Sclerotia survive on canes or in fruit mummies.Sclerotia survive on canes or in fruit mummies. Blossom debrisBlossom debris

► Sclerotia can survive adverse conditions.Sclerotia can survive adverse conditions.► Sclerotia germinate to produce conidia.Sclerotia germinate to produce conidia.► Conidial production favored by successive Conidial production favored by successive

interrupted wet periods.interrupted wet periods.► Conidia are dry and are dispersed by air Conidia are dry and are dispersed by air

currents or by water-splashing.currents or by water-splashing.

EpidemiologyEpidemiology

► Infection occurs in dead and senescing Infection occurs in dead and senescing flower parts and invades through the flower parts and invades through the stamens into the flower receptacle.stamens into the flower receptacle.

►Pathogen can also invade the necrotic Pathogen can also invade the necrotic areas around the abscission layer of the areas around the abscission layer of the shredded calyptra on the receptacle.shredded calyptra on the receptacle.

►Young berries generally resistant to Young berries generally resistant to infection due to epicuticular wax and infection due to epicuticular wax and chemicals in the wax.chemicals in the wax.

Why Disease??Why Disease??

► An outbreak of Botrytis bunch rot between An outbreak of Botrytis bunch rot between véraison and harvest is regulated by a véraison and harvest is regulated by a complex set of factors. complex set of factors. Of these, conidia dispersed in bunches and latent Of these, conidia dispersed in bunches and latent

infection established at the berry base or infection established at the berry base or receptacle during early season, and a stress receptacle during early season, and a stress factor(s), are the main factors responsible for factor(s), are the main factors responsible for symptom expression at véraison. symptom expression at véraison.

► Climatic conditions such as high humidity, Climatic conditions such as high humidity, dew and intermittent rain during late season dew and intermittent rain during late season will regulate bunch rot development.will regulate bunch rot development.

Botrytis cinereaBotrytis cinerea

► The fungus always attempts to penetrate The fungus always attempts to penetrate sound berries directly through the skin, but sound berries directly through the skin, but most of these penetrations are unsuccessful. most of these penetrations are unsuccessful.

► Skin damage (wind, birds, insects) thus also Skin damage (wind, birds, insects) thus also acts as a stress factor which offers another acts as a stress factor which offers another major pathway for the fungus to enter berries. major pathway for the fungus to enter berries.

► In the event of wounding, a combination of In the event of wounding, a combination of fresh wounds, freshly dispersed conidia and fresh wounds, freshly dispersed conidia and free water on the berry surface is necessary free water on the berry surface is necessary for successful wound infection. for successful wound infection.

► A synchronization and combination of these A synchronization and combination of these events may not commonly occur in the events may not commonly occur in the vineyard. vineyard.

SymptomsSymptoms

► Can occur as 2 epidemicsCan occur as 2 epidemics Early mostly asymptomatic and occurring from pre-Early mostly asymptomatic and occurring from pre-

bloom to fruit set.bloom to fruit set.► Brown-reddish lesions develop on leaves. Shoot dieback.Brown-reddish lesions develop on leaves. Shoot dieback.► Blossoms become latently infectedBlossoms become latently infected

However, not all infected blossoms result in diseaseHowever, not all infected blossoms result in disease

Later from pea-sized berries through harvestLater from pea-sized berries through harvest► Starts as browning of the skin of the fruit and invades other Starts as browning of the skin of the fruit and invades other

berries through cracks and wounds.berries through cracks and wounds. Berry leakageBerry leakage

► Dry weather=lesions cease expansionDry weather=lesions cease expansion► Wet weather=lesions continue to expand and fungus Wet weather=lesions continue to expand and fungus

moves to other berries thru spore movement or mycelial moves to other berries thru spore movement or mycelial growthgrowth

SymptomsSymptoms

►Poorly hardened shoots may show Poorly hardened shoots may show bleaching in the fall with development bleaching in the fall with development of black sclerotia forming in bleached of black sclerotia forming in bleached tissue.tissue.

►This occurs mostly around nodes and This occurs mostly around nodes and suggests entry of the fungus through suggests entry of the fungus through the petiole of a diseased leaf or through the petiole of a diseased leaf or through a leaf scar.a leaf scar.

►Sclerotia in mummified berries.Sclerotia in mummified berries.

SymptomsSymptoms

►Newly grafted grapevine cuttings held Newly grafted grapevine cuttings held in high humidity and at temperatures in high humidity and at temperatures of 30 C can be infected and quickly of 30 C can be infected and quickly destroyed by destroyed by Botrytis cinereaBotrytis cinerea..

►The fungus also may develop under The fungus also may develop under the paraffin used to seal the graft the paraffin used to seal the graft union of grafted vines and inhibits union of grafted vines and inhibits development of the graft union.development of the graft union.

Control of Botrytis Bunch RotControl of Botrytis Bunch Rot

►FungicidesFungicides►Leaf removalLeaf removal►Decreased fertilizer Decreased fertilizer ►Cluster ArchitectureCluster Architecture►TrellisingTrellising

FungicidesFungicides

►TimingTiming Bloom, Preclose, Veraison, PreharvestBloom, Preclose, Veraison, Preharvest

►ApplicationApplication Full coverage, Both sides of vine, PreventativeFull coverage, Both sides of vine, Preventative

►PhenologyPhenology Blossoms, young fruit, older fruit, leaves, Blossoms, young fruit, older fruit, leaves,

shootsshoots

►WeatherWeather RainRain

Table 1. Results of Grape (J. riesling) bunch rot fungicide trial in Philo, 2004. Fungicides were applied at bloom ‘A’, bunch close ‘B’, veraison ‘C’, and 1 week preharvest ‘D’.

1Severity is the percent of each cluster affected by Botrytis rot2Incidence is the percent of clusters with any rot.3Values in a column followed by the same letter are not significantly different according to Fisher’s LSD t test at P=0.05.

# Material, rate/A, application timing Severity, %1 Incidence, %2

4 Elevate 50WG, 1 lb, AB, fol/by Vangard 75WG, 10 oz, CD 0.05 c3 1.7 d3

13 Scala 606SC, 9 floz + Flint 50WG, 1.5 oz 0.06 c 1.7 d

12 Scala 606SC, 18 floz 0.14 c 1.7 d

5 Elevate 50WG, 1 lb, AB fol./by Pristine 38WG, 12.5 oz, CD 0.05 c 2.5 d

10 Rovral 75WG, 10.7 oz, A, fol/by A1664, 18.1 oz, BCD 0.07 c 3.3 d

8 Elevate 50WG, 1.5 lb 0.08 c 3.3 d

3 Elevate 50WG, 1 lb 0.13 c 3.3 d

6 Elevate 50WG, 1 lb + Quintec 250SC, 4 floz 0.09 c 4.2 d

16 Pristine 38WG, 12.5 oz 0.27 c 5.8 cd

15 Stylet Oil, 1% + Vangard, 75WG, 5 oz 0.28 c 5.8 cd

11 Vangard 75WG, 10 oz, AB 0.18 c 6.7 cd

18 Serenade AS, 5 qts, AC, alt/w Vangard 75WG, 10 oz, BD 0.29 c 10.0 cd

2 Rovral 75WG, 10.7 oz 0.38 c 10.0 cd

9 Rovral 75WG, 10.7 oz, A, fol/by A1664, 36.3 oz, BCD 0.48 c 10.0 cd

19 Vangard 75WG, 10 oz, CD 0.48 c 10.0 cd

14 Stylet Oil, 1% 0.65 bc 12.5 bcd

17 Serenade AS, 5 qts 0.51 c 15.8 abc

7 VigorCal II, 1 gal, AB, fol/by VigorK II, 1 gal, CD 1.23 b 21.7 ab

1 Untreated Control 2.06 a 24.2 a

Canopy ManagementCanopy Management

► Leaf RemovalLeaf Removal Effect on fungicide applicationEffect on fungicide application

► Increases target site hit by 200xIncreases target site hit by 200x► Timing=berry setTiming=berry set

Removes dead blossom debris, results in thicker wax layerRemoves dead blossom debris, results in thicker wax layer Later leaf removal results in sunburn, reduced epicuticular wax Later leaf removal results in sunburn, reduced epicuticular wax

thicknessthickness

► HedgingHedging Early Delays maturityEarly Delays maturity Late results in sunburn, Greenberry (Late results in sunburn, Greenberry (Cladosporium Cladosporium

cladosporioidescladosporioides))► Crown SuckeringCrown Suckering

Only small reduction in diseaseOnly small reduction in disease► VSPVSP

Excellent Botrytis control if clusters are exposedExcellent Botrytis control if clusters are exposed

Other Cultural PracticesOther Cultural Practices

► If caught w/o fungicide application and If caught w/o fungicide application and can get in the vineyardcan get in the vineyard Use spray rig to spray high pressure Use spray rig to spray high pressure

directed air at clustersdirected air at clusters►Interrupts infection processInterrupts infection process►Must be done within 12 hoursMust be done within 12 hours

► If you don’t leaf removeIf you don’t leaf remove Use leaf blower-type directed wind to Use leaf blower-type directed wind to

remove blossom debris early in seasonremove blossom debris early in season

Cluster ArchitectureCluster Architecture

►Tight clusters more prone to rotTight clusters more prone to rot Berry touch reduces the epicuticular wax Berry touch reduces the epicuticular wax

layer on the berry = easier access by layer on the berry = easier access by pathogen pathogen

Extend rachis??? Gib, DMI fungicidesExtend rachis??? Gib, DMI fungicides►Reduce touchingReduce touching

Early exposure to sunlightEarly exposure to sunlight►Increase wax thicknessIncrease wax thickness

FertilizersFertilizers

► Use of fertilizer can increase vegetativeness Use of fertilizer can increase vegetativeness Increase shadeIncrease shade

► Reduces wax thicknessReduces wax thickness Increase RHIncrease RH

► Reduces wax thicknessReduces wax thickness Decrease TemperatureDecrease Temperature

► Increases favorable conditions for pathogenIncreases favorable conditions for pathogen Reduce wind speedReduce wind speed

► Increases favorable conditions for pathogenIncreases favorable conditions for pathogen Increase succulence of tissueIncrease succulence of tissue

► Easier infection of tissue Easier infection of tissue

What Happened in 2006What Happened in 2006

►Rain during bloomRain during bloom►Rain preharvestRain preharvest►Hang timeHang time

Rachis began to senesce Rachis began to senesce ►Rachis infected resulted in berry dropRachis infected resulted in berry drop

Ripe fruit + water = RotRipe fruit + water = Rot Sound berries less effectedSound berries less effected

What to expect in 2007What to expect in 2007

► Botrytis epidemics cyclicBotrytis epidemics cyclic 3 year cycle3 year cycle 2007???2007???

► Longer fruit exposed on the vine the bigger Longer fruit exposed on the vine the bigger the chance of seeing diseasethe chance of seeing disease

► Early leafingEarly leafing► Fungicides if needed but always as a Fungicides if needed but always as a

preventative treatmentpreventative treatment Coverage!!! Best timing for good coverage is pre-Coverage!!! Best timing for good coverage is pre-

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